directory locking

Has anybody ever locked a directory using Windows 2000?

There is a folder on our shared network that a user wants to lockdown. I do not have experience doing so.

We have a Peer-to-Peer LAN using Win2000 with a Firewall; We do not use a Microsoft server.

A native solution would be grade, but if it cannot be done so, maybe somebody has bought a program to do this?